Medical procedures often require locating and treating target areas within a patient. Focused, dose-delivery radiation therapy requires locating the target with a high degree of precision to limit damaging healthy tissue around the target. It is particularly important to know or estimate the precise location of the target in radiation oncology because it is desirable to limit the exposure of adjacent body parts to the radiation in a patient already suffering the depredations of cancer. However, in all treatment procedures, whether radiologic or otherwise, it is most desirable to be able to accurately target a region to be treated.
In many applications, it is not possible to directly view a treatment target or portion thereof (such as, for example, a cancerous tumor, cyst, pseudocyst, or other target) that needs to be acted on in some manner. As one example, when treating a lung or pancreatic tumor with radiation, it may not possible to view the actual tumor within the patient immediately before the radiation treatment. It is therefore highly advantageous to have some mechanism for permitting the tumor to be located accurately so that the radiation treatment can be targeted at the tumor while avoiding damage to healthy tissue.
Even for target regions that may be visualized using CAT (computer-assisted tomography) scans, MRI (magnetic resonance imaging), x-rays, ultrasound, or other techniques, difficulties often arise in targeting a treatment. This is particularly true for target regions within a torso of a patient and soft tissue regions. Due to the mobility of tissues in those regions (e.g., movement of internal organs during respiration and/or digestion, the movement of breast tissue with any change of body position, etc.), a target region may not remain fixed relative to anatomical landmarks and/or to marks that can be placed onto an external surface of a patient's body during one of those visualization procedures.
Several techniques have been developed to address this problem. One such technique is to place markers into the patient along the margins of the target region. The markers may be active (e.g., emitting some kind of signal useful in targeting a therapy) or passive (e.g., non-ferromagnetic metallic markers—called fiducials—that can be used for targeting under ultrasound, MRI, x-ray, or other targeting techniques, which may be included in a treatment device).
A fiducial is typically formed of a radio-opaque material that the target can be effectively located and treated with a device that targets a site using the fiducials as positional markers under radiographic detection. Typically, the fiducials may be inserted into the patient during a simple operation. Percutaneous placement is most commonly used. However, use of minimally-invasive placement via an endoscope has recently developed for fiducial placement into a patient's internal organs. For example, percutaneous placement of fiducials along the margins of a pancreatic tumor can be complex and painful (particularly for obese patients, where the needle size is necessarily larger). Another process using percutaneously implanted objects in a patient is brachytherapy. In brachytherapy, radioactive sources or “seeds” are implanted into and/or adjacent a tumor to provide a high dose of radiation to the tumor, but not the healthy tissue surrounding the tumor.
FIGS. 1A and 1B show longitudinal sectional views of a two-piece introducer 100 of the prior art useful for placement of brachytherapy seeds or fiducials. Referring first to FIG. 1A, the introducer 100 includes a needle 102 and a stylet 104 slidably disposed within the needle 102. The stylet 104 includes a first handle 101 and a blunt distal end 106. The needle 102 includes a second handle 103 and a bevel-tipped cannula 108 extending through the second handle 103. The cannula 108 is configured to hold a seed/fiducial 110. The cannula 108 has a distal tip 105 configured for percutaneous implantation of the seed/fiducial 110 into the patient.
In a “pre-loaded configuration,” the seed/fiducial 110 is retained in the cannula 108 by a plug 112 made from bone wax or other suitable bio-compatible material(s). This is typically accomplished by a “muzzle-loading” technique where the fiducial is placed into the distal needle and then held in place by the bone wax plug. This can present some challenges, as the bone wax plug 112 can be visible as an artifact in the patient, potentially interfering with clear visualization of body structures or treatment devices. With this configuration, the cannula 108 must be withdrawn and reloaded after delivery of each seed/fiducial 110. If the target locations for the fiducials are very far apart, use of a single percutaneous introducer cannula/trocar for multiple introductions of the cannula 108 may not be possible. In such a circumstance, the patient must endure several percutaneous punctures (and the increased attendant risk of infection for each).
To implant the desired arrangement of seeds/fiducials 110 at a target location in a patient, an operator pushes the cannula 108 in a first direction (arrow A) to insert the tip 105 into the patient (typically under fluoroscopic visualization). The operator then pushes the second handle 103 further in the first direction to position the tip 105 at the desired depth within the patient where a seed/fiducial 110 is to be implanted. Throughout this motion, the operator moves the needle 102 and the stylet 104 together as a unit. At the desired depth/location, the operator grasps the first handle 101 with one hand and the second handle 103 with the other hand. Then, the operator holds the first handle 101 stationary while simultaneously sliding the second handle 103 back in a second direction (arrow B) toward the first handle 101. As shown in FIG. 1B, this movement causes the cannula 108 to retract over the seed/fiducial 110 to implant it in the patient. Alternatively, the operator may move the first handle 101 in the first direction (arrow A) while sliding the second handle 103 back in the second direction (arrow B). This causes the stylet 104 to push the seeds 110 out of the cannula 108. The procedure is then repeated to place other seeds/fiducials 110. When being used for targeting of radiation therapy, a minimum of three fiducials is typically required.
One potential issue that may arise is the premature deployment of fiducials. This may occur prior to the user deploying the fiducial(s) at a target site, for example if the stylet 104 undergoes inadvertent distal movement relative to the cannula 108. Premature deployment of fiducials may occur during manufacturing, shipping, or handling immediately prior to use, to name a few common examples. Solutions to this problem may also have practical limitations, for example, certain structures may not be feasible or cost effective given certain manufacturing environments (e.g., molding vs. 3D printing) and materials (e.g., plastics vs. metals).
It would be desirable to use ultrasound, and particularly endoscopic ultrasound (EUS) for navigation and placement of fiducials. As such it would be desirable to provide and use the largest possible fiducial that will provide improved echogenicity based on its size and echogenic profile. It would be desirable to provide multiple fiducials in a needle that can be introduced in a controlled serial manner (one, or some other pre-determined number, at a time) rather than requiring manual reloading after placement of each fiducial. It would further be desirable to provide such a system with features that will effectively prevent premature and/or undesired fiducial deployment.